Sudden cutting-out
I am tearing my hair out with my 1995 Jaguar XJ6 X300 3.2 auto, with full service history and 88,000 miles. It will start and run from cold perfectly for 55-60 minutes, then it stops without any prior warning, bringing up the EML and battery lights. The engine will restart immediately, but the fault will then reoccur at ever-shorter intervals. There is now some irregular running and misfiring. The following items have been checked: All earth and electrical connections. Fuel pump, fuel pump relay and fuel filter. The fuel pressure regulator has been replaced and the fuel pressure tested. All relays and the fuseboard. The battery has also been replaced. The cam sensor, crank sensor and six coil packs have been replaced. The collision cut-out switch was tested and found to be OK.
None of this has failed to eliminate the fault, which still occurs at between 55-60 minutes whether the vehicle is driven or stationary.
As a last resort, the car was booked into the main agent for a full diagnostic check. They had the vehicle for five days but were unable to come up with anything.
I am sure the problem is heat-related, but what could it be? Peter Tomkins Given the circumstances of the failure, the problem does appear to be associated with the heat of the engine. You also seem to have replaced just about every component that could be the source of the problem. There is always the possibility that one of the components you have replaced is also faulty and this can really make diagnosis difficult, but I am assuming you have replaced all the above items with either new or tested components. If not, the problem still sounds like the crankshaft sensor has issues.
Taking it that all the replacement parts are good and not a concern, this leads me to believe the problem must lie within the wiring system, with the most likely source being either the loom from the crankshaft sensor or the multi-plug on the ECU. Testing the system with an ohmmeter one wire at a time will be a laborious task, but may highlight the fault.
You have not mentioned connecting the vehicle up to a scanner and your XJ6 should have a 16-pin data connector under the dashboard. This may help retrieve a code that could point you in the right direction.